The progenitor system(s) as well as the explosion mechanism(s) of thermonuclear (Type
Ia) supernovae are long-standing issues in astrophysics. Here we present ejecta masses
and other physical parameters for 28 recent Type Ia supernovae inferred from multiband
photometric and optical spectroscopic data. Our results confirm that the majority
of SNe Ia show {\\it observable} ejecta masses below the Chandrasekhar-limit (having
a mean $M_{\\rm ej} \\approx 1.1 \\pm 0.3$ M$_\\odot$), consistent with the predictions
of recent sub-M$_{\\rm Ch}$ explosion models. They are compatible with models assuming
either single- or double-degenerate progenitor configurations. We also recover a sub-sample
of supernovae within $1.2 $ M$_\\odot$ $< M_{\\rm {ej}} < 1.5$ M$_\\odot$ that are
consistent with near-Chandrasekhar explosions. Taking into account the uncertainties
of the inferred ejecta masses, about half of our SNe are compatible with both explosion
models. We compare our results with those in previous studies, and discuss the caveats
and concerns regarding the applied methodology.
